From ae1a8d47edae9cb2d76494af62cb505abfbd2933 Mon Sep 17 00:00:00 2001
From: Ilya Tevrukov <tevrukovila@gmail.com>
Date: Fri, 7 Nov 2025 13:58:41 +0000
Subject: [PATCH] Fixed binary search algorithm, changed 'left < right' to
 'left <= right'. Added comprehensive test suite for binary search.
 Implemented ISBN validator utility. Fixed weight calculation from 'weight =
 10' to 'weight = 10 - i'. Added necessary input validation and error
 handling. Extended test coverage for all components.

---
 src/bin_search.py      | 23 ++++++++++++-----------
 src/checksum.py        | 39 +++++++++++++++++++++++++--------------
 test/test_bin_searh.py | 36 +++++++++++++++++++++++-------------
 test/test_checksum.py  | 30 +++++++++++++++++++++---------
 4 files changed, 81 insertions(+), 47 deletions(-)
 mode change 100644 => 100755 src/bin_search.py
 mode change 100644 => 100755 src/checksum.py
 mode change 100644 => 100755 test/test_bin_searh.py
 mode change 100644 => 100755 test/test_checksum.py

diff --git a/src/bin_search.py b/src/bin_search.py
old mode 100644
new mode 100755
index 713abfc..70dc95a
--- a/src/bin_search.py
+++ b/src/bin_search.py
@@ -1,11 +1,12 @@
-def binSearch(xs: list[int], x: int):
-    left, right = 0, len(xs) - 1
-    while left < right:
-        mid = (left + right) // 2
-        if xs[mid] == x:
-            return mid
-        if xs[mid] < x:
-            left = mid + 1
-        else:
-            right = mid - 1
-    return -1
+def binSearch(xs: list[int], x: int):
+    xs = sorted(xs)
+    left, right = 0, len(xs) - 1
+    while left <= right:
+        mid = (left + right) // 2
+        if xs[mid] == x:
+            return mid
+        if xs[mid] < x:
+            left = mid + 1
+        else:
+            right = mid - 1
+    return -1
diff --git a/src/checksum.py b/src/checksum.py
old mode 100644
new mode 100755
index 74b4fb0..654d9a8
--- a/src/checksum.py
+++ b/src/checksum.py
@@ -1,14 +1,25 @@
-def modulo11Checksum(ISBNNumber: str):
-
-    digits = [int(char) for char in ISBNNumber if char.isdigit()]
-
-    checkDigit = digits[-1]
-
-    total = 0
-    for i in range(len(digits) - 1):
-        weight = 10
-        digit = digits[i]
-        total += digit * weight
-
-    checksum = total + checkDigit
-    return checksum % 11 == 0
+def modulo11Checksum(ISBNNumber: str):
+    digits = [int(char) for char in ISBNNumber if char.isdigit()]
+    if len(digits) != 10:
+        return -1  
+    checkDigit = digits[-1]
+    total = 0
+    for i in range(len(digits) - 1):
+        weight = 10 - i
+        digit = digits[i]
+        total += digit * weight
+    checksum = total + checkDigit
+    return checksum % 11 == 0
+
+ISBNNumber = input()
+
+while ISBNNumber != '-1':
+    res = modulo11Checksum(ISBNNumber)
+    if res == 1:
+        print('correct')
+    elif res == -1:
+        print('Incorrect number length')
+    else:
+        print('incorrect')
+    ISBNNumber = input()
+    
diff --git a/test/test_bin_searh.py b/test/test_bin_searh.py
old mode 100644
new mode 100755
index d18d85b..9a7a50a
--- a/test/test_bin_searh.py
+++ b/test/test_bin_searh.py
@@ -1,13 +1,23 @@
-from src.bin_search import binSearch
-
-
-def test_middle():
-    assert binSearch([1, 2, 3, 4, 5], 4) == 3
-
-
-def test_start():
-    assert binSearch([1, 2, 3, 4], 2) == 1
-
-
-def test_not_in_list():
-    assert binSearch([1, 2, 3, 4], 5) == -1
+from src.bin_search import binSearch
+def test_middle():
+    assert binSearch([1, 2, 3, 4, 5], 4) == 3
+
+
+def test_start():
+    assert binSearch([1, 2, 3, 4], 2) == 1
+
+
+def test_last_element():
+    assert binSearch([1, 2, 3, 4, 5], 5) == 4
+
+
+def test_single_element_found():
+    assert binSearch([42], 42) == 0
+
+
+def test_single_element_not_found():
+    assert binSearch([42], 100) == -1
+
+
+def test_empty_array():
+    assert binSearch([], 5) == -1
diff --git a/test/test_checksum.py b/test/test_checksum.py
old mode 100644
new mode 100755
index f64a64c..ffad878
--- a/test/test_checksum.py
+++ b/test/test_checksum.py
@@ -1,9 +1,21 @@
-from src.checksum import modulo11Checksum
-
-
-def test_good():
-    assert modulo11Checksum("2-266-11156-8")
-
-
-def test_bad():
-    assert not modulo11Checksum("2-266-11156-3")
+from src.checksum import modulo11Checksum
+
+
+def test_bad():
+    assert not modulo11Checksum("2-266-11156-3")
+
+
+def test_good_without_hyphens():
+    assert modulo11Checksum("2266111568")
+
+
+def test_good_with_x_check_digit():
+    assert modulo11Checksum("0-304-33376-")
+
+
+def test_bad_wrong_length_long():
+    assert modulo11Checksum("1234567890123") == -1
+
+
+def test_bad_wrong_length_short():
+    assert modulo11Checksum("12345") == -1